External fixation system

Abstract

An external fixation system comprising: first and second planar at least part-circular ring elements, the first ring element having a circumferential track extending along the part-circular circumference thereof; a plurality of struts each having a first and second end, the first end of each strut coupled to the first ring by a first connector and the second end of each strut coupled to a second ring by a second connector, the first connector including a spherical joint; the second connector non-rotatably coupled to the second ring, the strut second end being coupled to the second connector by a U-joint; shuttles mounted on the track of the first ring for movement there along with one shuttle coupled to each strut; and means for controlling the angular position of each strut second end and means for controlling the position of each shuttle along the circumferential track on the first ring.

1. An external fixation system comprising:
 first and second ring elements, the first ring including a gear track around a circumference thereof; 
 three shuttles mounted on the first ring element for controlled movement about a circumference of the first ring element each shuttle having a first connector including a joint having three degrees of freedom and the system having three second connectors fixed to the second ring, the three shuttles having a gear engaging the gear track on the first ring; 
 three kinematic chains each having first ends connected to a respective shuttle by the first connector and a second end connected to a respective second connector, the second connector non-rotatably mounted on the second ring, the second connector having a universal joint freely rotatable about a first axis parallel to the second ring element and rotatable in a controlled manner about a second axis perpendicular to the first axis; and 
 drive means for controlling the movement of each shuttle about the circumference of the first ring and for controlling the movement of the kinematic chain second end about the second axis of the second connector on the second ring. 
 
     
     
       2. The external fixation system as set forth in  claim 1  wherein the joint having three degrees of freedom is a spherical joint. 
     
     
       3. The external fixation system of  claim 1  wherein the drive means for controlling the position of the shuttle comprises a computer controlled drive motor for rotating the shuttle gear. 
     
     
       4. An external fixation system comprising:
 first and second planar at least part-circular ring elements, centers of the first and second ring elements spaced along an axis, the first ring element having a circumferential gear track extending along the part-circular circumference thereof; 
 three and only three struts each having a first and second end, the first end of each strut coupled to the first ring by a first connector and the second end of each strut coupled to the second ring by a second connector; 
 the second connector at the second end of each strut having a universal joint allowing rotation about a first axis parallel to the plane of the second ring and rotation about a second axis perpendicular to the first axis; 
 the first connector including a shuttle mounted on the track of the first ring for movement therealong and a joint having three degrees of freedom coupled to the first end of each strut, the shuttle having a gear engaging the gear track on the first ring; and 
 drive means for controlling the angular position of each strut second end about the second axis and drive means for rotating the shuttle gear for controlling the position of each shuttle along the circumferential gear track on the first ring. 
 
     
     
       5. The external fixation system as set forth in  claim 4  wherein the first and second rings are complete circles. 
     
     
       6. The external fixation system as set forth in  claim 5  wherein the shuttles are spaced at predetermined locations around a circumference of the first ring. 
     
     
       7. The external fixation system as set forth in  claim 6  wherein each shuttle can move along the track on the ring in predetermined increments. 
     
     
       8. The external fixation system as set forth in  claim 4  wherein the struts are of variable length and include means for locking the strut at a desired length. 
     
     
       9. The external fixation system as set forth in  claim 4  wherein the struts are of a fixed length. 
     
     
       10. The external fixation system as set forth in  claim 4  wherein the joint having three degrees of freedom is a spherical joint. 
     
     
       11. The external fixation system of  claim 4  wherein the drive means for controlling the position of the shuttle comprises a computer controlled drive motor for rotating the shuttle gear.